Spark plug shielding



April l2, 1938.

T. HISCOCK SPARK PLUG SHIELDING Filed Jan. 6, 195o ATTORNEY l Patented Apr. '412,

PAT-ENT ori-lcs smak rLUG 'smmmmc Tho Hiscock, Seattle, Wash., assigner, by mesne gnments, to United Aircraft Oorporatioma corporation of Delaware Appumxon January s, 1930, semina. 418,951; s cwms (ci. iss-iss) This ,invention relates to improvements in shielding vapparatus for spark plugs and `ignition systems as used in internal combustion engines.

I'he principal object of the invention is to pro- 5 vide a means for suppressing interference with radio reception in a vehicle caused by the spark plugs and electricalsystems during operation of the radio receiving apparatus while the engine is running. l

This and other objects will appear as my invention is more fully hereinafter described in the following specication, illustrated in theA accompanying drawing and finally pointed out in the appended claims. 1g Figure iy is a rear elevation of a radial, -aircooled aircraft engine, showing theembodiment or my improved iorm of shielding apparatus.

Figure 2 is an enlarged sectional detail view or a detachable spark plug shield.

Figure 3 is a sectional view taken on the line 3-3 of Figure 2.

' Referring now more particularly to the drawing: K Reference numeral Iv indicates an internal u 'combustion engine oi the radial air-cooled type, having two magnetos land I, and spark plugs 4. There are two spark plugs in each cylinder. This arrangement is known as a double ignition system. n The shielding apparatus consists ofv a circular conduit l which is secured to the back of the engine by any suitable means. such for instance, as brackets 1 and bolts I. Outlets 0 are formed around the outer periphery ol the conduit.A Inlets i0 are formed on the inner periphery of the conduit to receive nine wires, indicated' at Ila, from each of. the magnetos. The wires are divided into two groups of four and tive. Each group coming from the magneto is shielded orcovered 4o with wire mesh as indicated at I i, up to the point where they come together and extend through a hollow exible tube I3 which is secured to the inlet by a clamp i3. In like manner the outlets are provided with hollow. ilexible tubes il '46 which are internally lined with 'wire mesh as shown in Figure 2. Their outermost ends connect with a hollow and rigid tube Il by means 1 oi a Aclamp or the like, as indicated at Il. I'he opposite end of the tube Il is made integral with 50 a metallic`spring cap I1 which consists of a hollowrcylindrical body member which is enlarged eas shown and slotted in the direction of its length,

as'indica'ted at I8. At its outermost end, the cap is formed with an annular-groove Ita, which 65 makesI an internally projecting Irib adaptedto l approved manner, as for example, by means .casing said conductor, a metallic cap iit within a groove 23. This construction constitutes a quick-detachable connection in the lsense that no member need be unscrewed to remove the cap I1 or disconnect ,the spark plug wire, and

no member need be screwed up when replacing` the cap or again connecting the ignition wire to the spark plug. The interior of the cap is partly filled with insulating material i9 to prevent the spark plug from grounding with'the cap. Il in dicates a spark plug of conventional design exm cept i'or a nut 2| with an outwardly extending tubular sleeve 22 .which is formed with an annu- )lar groove 23, adapted to co-operate with the internal rib made by the groove ita in the body member when the cap is firmly mounted in place u on the plug.

The wires Ila coming iromthe magnetos extend through the conduit and branch out in pairs, as' shown, to connect with the spark plugs. .e The connection with the plug is made in any m oi a screw; 2l which is embedded in the wire and backed by a coil spring 25 to iorm contact with the plug under spring tension.

While I have shown a particular form of embodiment I am aware that many minor changes thereinv will readily suggest themselves to others skilled in the art without departing from the spirit and scope of the invention.

Having thus described the invention, what I o claim as new and desire to protect by Letters Patent is:-

l. In a radio shielding means for motor ignition devices, in combination with a metallic shield encasing a conductor, a metallic cap seu cured to an end or said shield, a sleeve-adapted -to project outwardly from the outer end oi a spark plug body, and the cap' and Ysleeve having an interengaging circumferential groove and rib J whereby the cap may be retained upon a spark plug, and grounded thereto.

2r In a radio shielding means formotor ignition devices, in combination with wire, a metallic shield insulated from andensecured to 4g an end of'said shield, a sleeve adapted to project outwardlyirom the'outer end oi a sparkA plug body, means interengageable by longitudinal movement of the cap relative to the sleeve for detaohably retaining the cap upon and ground- 50 ing it to the sleeve, and a spring-urgedcontact point received in the` end of the conductor, and. having limited longitudinal movement within the cap, to contact. with the electrode otra spark plug upon which the cap is secured.' l v 55 3. In a radio shielding means for motor ignition devices, in combination with a conducting wire, a metallic shield insulated from and encasing said conductor, a metallic cap secured to an end of said shield, a sleeve adapted to project out' wardly from the louter end of a spark plug body, an insulator received within the cap, and internally recessed to receive the spark plug outwardly of said sleeve, and shouldered outwardly thereof, a contact within the recess and connected through the insulator with the end of the conductor, to connect the two electrically and to prevent separation of the insulator and the cap. a spring seated upon said shoulder of the insula tor tofpress the contact into engagement with the end of the spark plug electrode, and means lnterengageable between the cap and sleeve by relative axial movement to retain the cap, insulator, and contact upon the sleeve.

4. In combination, a spark plug comprising an insulator, and a metal supporting shell, a metallic sleeve of smaller external diameter than said shell attached to said shell and extending out-f wardly therefrom, a solid dielectric located between said insulator and said sleeve and extending outwardly beyond said insulator, a metallic cap encircling said dielectric and said sleeve and having spring pressed means coacting with said sleeve for holding said cap 4and said dielectric in position.

5. In a radio shielding means for motor ignition devices, in combination with a conducting wire, a metallic shield insulated Iromand encasing said conductor, a metallic cap secured to an end of said shield, a sleeve adapted to project outwardly from the outer end of a spark plug body, means interengageable by longitudinal movement of the cap relative to the sleeve for detachably retaining the cap upon and grounding it to the sleeve, a solid dielectric seated in said cap and located inside said sleeve when thecap and sleeve are in assembled relation, and a spring urged contact point received in the end of the conductor, and having a. limited longitudinal 20 

